Image sensors with noise reduction

ABSTRACT

In various embodiments, image sensors and methods of operating the image sensors are disclosed. In an example embodiment, a pixel circuit having a first electrode is coupled to a reset transistor and to a first region of an optically sensitive layer, and a second electrode is coupled to a pixel sense node and to a second region of an optically sensitive layer. The electrical path from the first electrode, through the optically sensitive layer, and into the second electrode functions as a variable resistor. Other devices and methods of operating the devices are disclosed.

PRIORITY CLAIM

The present application claims the benefit of priority of U.S.Provisional Patent Application Ser. No. 62/031,695, filed Jul. 31, 2014,entitled “IMAGE SENSORS WITH NOISE REDUCTION,” which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present application relates generally to the field of optical andelectronic systems and methods, and methods of making and using thedevices and systems.

BACKGROUND

Image sensor noise is comprised of fixed pattern noise (FPN) or temporalnoise. FPN can be mitigated via offset and gain correction schemes.This, however, is not true for temporal noise. Once introduced, itremains in the image. Hence, temporal noise reduction techniques arerequired.

A major contributor of temporal noise in 3T pixels is reset noise with anoise power on the order of kT/C, where C is the capacitance at thesense node of the pixel. Reset noise results from random fluctuations involtage at the sense node due to intrinsic noise in the resettransistor. These fluctuations are frozen on the sense node when therespective capacitance is disconnected from reset device. Reset noisecan be suppressed by reducing the amount of these fluctuations. Belowdescribes a method to reduce this component.

The noise reduction technique makes use of a column feedback amplifierand a tapered reset signal. The fluctuations on the sense node arereduced by sensing the variations instantaneously and adjusting thedrain current by modulating gate of the reset transistor. The resetsignal modulates the amplifier loop traversing hard reset and soft resetresulting in a noise power that is reduced by the open loop gain of theamplifier, i.e. kT/AC (where A is the amplifier gain), with low lag.

Moreover new techniques can be implemented if a photo-sensitivematerial, i.e. quantum film, is used instead of an integrated siliconphotodiode, as the sense node is comprised of the electrical and siliconparasitic capacitance as well as the photosensitive materialcapacitance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example embodiment of a reset noise reduction circuit;

FIG. 2 shows an example embodiment of a reset noise circuit;

FIG. 3 shows an example embodiment of a film noise circuit including across section of a reset methodology that uses an electrode instead of areset transistor;

FIG. 4 shows an example embodiment of a 3T pixel architecture;

FIG. 5 shows an example embodiment of six different reset electrode (RE)positioning options in an optically sensitive layer stack;

FIG. 6 shows an example embodiment of a pixel architecture for anoptically sensitive layer reset and noise reduction circuit;

FIG. 7 shows an example embodiment of a timing diagram for an opticallysensitive layer reset and noise reduction circuit that may be used withthe circuit of FIG. 6;

FIG. 8 shows an example embodiment of a pixel architecture for noisereduction using a reset transistor MRES;

FIG. 9 shows an example embodiment of a pixel architecture for noisereduction using a reset transistor MRES with the drains of the reset(MRES) and source follower (MSF) being electrically coupled;

FIG. 10 shows an example embodiment of a timing diagram for a noisereduction pixel architecture using a reset transistor MRES that may beused with the circuits of FIGS. 8 and 9;

FIG. 11 shows overall structure and areas related to a quantum dot pixelchip, according to an embodiment;

FIG. 12 shows an example of a quantum dot;

FIG. 13 shows a two-row by three-column sub-region within a generallylarger array of top-surface electrodes;

FIG. 14 illustrates a 3T transistor configuration for interfacing withthe quantum dot material;

FIG. 15 is a block diagram of an example system configuration that maybe used in combination with embodiments described herein;

FIG. 16 shows an embodiment of a single-plane computing device that maybe used in computing, communication, gaming, interfacing, and so on;

FIG. 17 shows an embodiment of a double-plane computing device that maybe used in computing, communication, gaming, interfacing, and so on;

FIG. 18 shows an embodiment of a camera module that may be used with thecomputing devices of FIG. 16 or FIG. 17;

FIG. 19 shows an embodiment of a light sensor that may be used with thecomputing devices of FIG. 16 or FIG. 17;

FIG. 20 and FIG. 21 show embodiments of methods of gesture recognition;

FIG. 22 shows an embodiment of a three-electrode differential-layoutsystem to reduce external interferences with light sensing operations;

FIG. 23 shows an embodiment of a three-electrode twisted-pair layoutsystem to reduce common-mode noise from external interferences in lightsensing operations;

FIG. 24 is an embodiment of time-modulated biasing a signal applied toelectrodes to reduce external noise that is not at the modulationfrequency;

FIG. 25 shows an embodiment of a transmittance spectrum of a filter thatmay be used in various imaging applications;

FIG. 26 shows an example schematic diagram of a circuit that may beemployed within each pixel to reduce noise power; and

FIG. 27 shows an example schematic diagram of a circuit of aphotoGate/pinned-diode storage that may be implemented in silicon.

DETAILED DESCRIPTION

Various embodiments of the disclosed subject matter describe imagesensors with noise reduction. For example, FIG. 1 shows an exampleembodiment of a reset noise reduction circuit. As shown in FIG. 1, RSTrepresents a signal applied to the gate of transistor M_(RST), whichshall be referred to as the reset transistor. The drain is connected tothe output of a column feedback amplifier. Replacing the typicalphoto-conversion element is Quantum Film (QF). The source of M_(RST) isconnected to the QF element and the input gate of source followerdevice, M_(SF).

V_(DRAIN) is the voltage which regulates the amplifier loop therebymaking V_(COL) equal to V_(REF). The following expression describesV_(DRAIN):

V _(DRAIN) ≈V _(REF) +V _(DROP) +V _(GS)(M _(RST))  (1)

As an example, for a 110 nm CMOS Image Sensor process a typical valuefor V_(DRAIN) is about 0.8 V to about 1.5 V with active feedback.

V_(SN) is the voltage of the sense node which is also the source of theaforementioned transistor M_(RST). While the feedback loop is active,V_(SN)≈V_(DRAIN).

Normally, in the absence of the feedback-based reset scheme describedherein, the timing of the circuit functions as follows. Referring to anexample embodiment of a reset noise circuit of FIG. 2, as RST and HR(hard reset) are high, V_(SN) is reset to approximately 1.6 V. As HRgoes low, a soft reset (SR) is entered and V_(SN) slowly moves towardthe pixel supply voltage (V_(PIX)). Using HR/SR reduces noise power fromkT/C to approximately kT/2C. In the dark V_(SN) integrates down at arate determined by the dark current. Ideally, this is a small value ofabout 10 electrons/s, which for a conversion gain of 88 μV/e⁻,corresponds to a rate of approximately 0.8 mV/s. A conversion gain of 88μV/e⁻ would result in 16e⁻ of noise.

With the feedback-based implementation, as the pixel is selected (SEL ishigh) a reset signal is applied (RST). The RST is comprised of threeareas of operation—hard reset (HR), soft reset (SR), and off (freeze).During HR phase V_(SN) is reset to approximately 1.8V. HR of the pixelremoves image lag. As RST is tapered, the system inters into the SRphase. Through HR/SR the high gain amplifier adjusts V_(DRAIN) to createa virtual ground at the inputs of the amplifier by makingV_(COL)=V_(REF)=1.4 V. In the process, the high gain negative feedbackcompensates for any fluctuations at the sense node, resetting V_(SN)with a noise power less than kT/C. The pixel does not reach equilibriumbut is held in SR mode under continuous feedback. When RST is low, thenoise at the sense node is frozen. A conversion gain of 88 μV/e⁻ andopen loop gain of 1000 V/V will result in less than 10e⁻ of noise.

To reduce row time the RST time slot should be as small as possible. Thetime slot should be distributed such that the SR portion is as large aspossible, as this is the time when the noise reduction takes place. TheHR time will be determined by the loop response as V_(COL) reachesV_(REF) within a desired level of accuracy. As you move through SR, theresistance of the RST device increases (that is, modulated bandwidth)and ultimately opens the loop and thereby freezes a voltage at the sensenode (V_(SN)). V_(COL) will be a level-shifted version of this reducednoise V_(SN). In one example, less than 3.5 μs is required for 10e⁻ ofnoise.

In embodiments, the reset of the sense node is not implemented with asilicon transistor device but uses a dedicated photosensitive materialelectrode to flush the charge out. FIG. 3 shows a cross section of areset methodology that uses an electrode instead of a reset transistor.In this implementation, the second photo-sensitive material electrode,which would normally be biased to a constant DC voltage, is, instead,during the reset phase, driven by the feedback amplifier, and providesan electrical path to close the loop and enable the noise loweringtechnique.

FIG. 4 shows how an optically sensitive layer can be employed as a lightsensitive device when integrated with a 3T pixel architecture. In FIG.4, the sense-node electrode (SE) is in electrical communication with thesense node (SN). Incoming photons induce the generation of carrierswithin the optically sensitive material. In embodiments, the opticallysensitive layer may comprise, for example, quantum dots, organics,polymers, bulk solution-processed semiconductors, bulk crystallinesemiconductors such as crystalline silicon, or nanowires, nanoplates, orquantum dots.

Photocarriers are collected at the sense-node electrode as it is leftfloating during the integration period. This causes the potential of thesense node to change at a rate proportional to the light intensity. Whenthe optically sensitive material is integrated in a 3T pixelarchitecture, a major contributor of temporal noise is Johnson-Nyquistnoise. Johnson-Nyquist noise is due to the thermal fluctuations ofcharge carriers within the reset transistor channel during the resetoperation of the sense node. It causes the reset level to be differentfrom reset to reset, for example, from frame to frame in an imagesensor. The noise power of the reset operation is on the order of kT/C,where C is the capacitance of the sense node.

In order to reset the sense node, an electrical connection between thesense node and a regulating power supply is typically established. Thisis traditionally achieved via a reset transistor (M_(RES)) located inthe pixel pitch (see FIG. 4).

Alternative approaches can be used to achieve this electricalconnection. Desirably, in such approaches, the resistive propertiesbetween sense node and regulating supply can toggle between very highresistivity (open circuit) to very high conductivity (closed circuit).

In embodiments of the disclosed subject matter, the controllably-varied(toggled) connection is achieved, and regulated, within the opticallysensitive layer. Embodiments of an optically sensitive layer include onecomprised of quantum dots. In embodiments, the optically sensitive layeroperates as a nonlinear light-sensitive device whose resistance dependson the voltage bias across two electrodes.

FIG. 5 shows example configurations of electrodes pairs that may beemployed in the regulation of the conductance of the connection referredto above. In an embodiment, FIG. 5 shows an example of six differentreset electrode (RE) positioning options in an optically sensitive layerstack.

With continuing reference to FIG. 5, SE stands for Sense-node Electrodewhile RE stands for Reset Electrode. These two electrodes can rely on anumber of possible layouts, materials, fabrication techniques, andproperties. By controlling the bias voltage across these two electrodes,the optically sensitive layer can be operated in different regimes. Inparticular, the optically sensitive layer may be designed to behave as anonlinear resistor device, one that exhibits high conductivity (e.g.,kΩ−MΩ−GΩ) at high bias voltage (e.g., about 2 V to about 3 V), and thatexhibits high resistivity (e.g., approximately 10¹²Ω to 10¹⁸Ω) at asmall bias voltage (e.g., about 0 V to about 1 V).

The resistance between any two electrodes contacting the opticallysensitive layer can be tuned by adjusting the bias between the twoelectrodes. The optically sensitive layer can be a semiconductor device,similar to a pn-junction, such that its current-voltage behavior ishighly nonlinear. With low to moderate biasing in one polarity (called“reverse bias” here), the optically sensitive layer resistance can be inthe range of approximately 10¹²Ω-μm² to 10¹⁸Ω-μm². When biased in theopposite polarity (called “forward bias” here), the optically sensitivelayer resistance can be in the range of approximately 10³Ω-μm² to10⁹Ω-μm², with an exponential bias dependence so that the opticallysensitive layer resistance drops dramatically with increasingly largerforward biases.

Noise reduction techniques can make use of a feedback amplifier (e.g., aLow Noise Amplifier, LNA) and a device to modulate the pixel noisebandwidth. The fluctuations on the sense node are reduced by sensing theREADBUS (see FIG. 6) variations at the input of the amplifier that willadjust its output to modulate the sense node voltage and correct for thenoise fluctuations. Typically the amplifier compensates for noisefluctuations that are present on its input lines (i.e., that have notbeen filtered out by the bandwidth of the feedback loop). Therefore, toensure maximum noise reduction, the bandwidth of the pixel noisefluctuations needs to be lower than the bandwidth of the feedback loop(BW_(noise)<BW_(feedback)). The pixel bandwidth on the sense node can becontrolled by connecting a nonlinear resistor device to the sense node.Its resistance will determine the final bandwidth of the sense node. Inparticular a higher resistance will yield lower pixel bandwidth.

One way to modulate the bandwidth of the sense node is by using theoptically sensitive layer as a variable resistor. The resistance of theoptically sensitive layer can be tuned by the proper choice of biasing,so that it can provide the approximately 1 kΩ to 10 kΩ used during thereset phase, the approximately 1 GΩ to 10 GΩ (giga-Ohm) used during avariable high resistance state, and the greater than approximately 10¹⁶Ωused during the “off” state.

A resistance of approximately 1 kΩ to 10 kΩ can be achieved with aforward bias of approximately 1 V to 2 V, a resistance of approximately1 GΩ to 10 GΩ (giga-Ohm) can be achieved with a forward bias ofapproximately 0.1 V to 1 V, and a resistance of greater thanapproximately 10¹⁶Ω can be achieved with a reverse bias of approximately1 V to 3 V.

The resistance of the optically sensitive layer can be adjusted throughcontrol of the pixel geometry. Increasing the separation of the pixelelectrode and reset electrodes to the optically sensitive layer willincrease the optically sensitive layer resistance, while increasing thearea of each electrode will reduce the optically sensitive layerresistance. The optically sensitive layer resistance can also becontrolled by changes to the device architecture of the opticallysensitive layer device stack, including choices of electrode materials,interfacial layers, and composition and processing of the opticallysensitive layer. These choices can modulate the rate of currentinjection from the electrodes, as well as the transport andrecombination processes in the optically sensitive layer, all of whichaffect the voltage-dependent resistance of the optically sensitivelayer.

In embodiments, it is possible to use a MOS transistor to reset the SN,whose channel resistance is changed by varying the potential on the gateof the transistor (see FIG. 8). An example timing sequence for thispixel architecture is shown in FIG. 10.

In embodiments, the drain of the reset MOS device can be shared with thedrain of the source follower device (see FIG. 9). The operation of thispixel architecture is similar to that described in FIGS. 8 and 10;however, it removes the need for an additional metal line connectioninto the pixel (the transistor M_(SF) being now driven by CONTROL BUS),thus enabling a smaller pixel pitch.

When the reset element is in low resistance mode, the sense node isfast, and the noise therefore has a high frequency bandwidth. However,since the column node is generally very slow, the full spectrum of thenoise on the sense node cannot be seen at the terminals of the LNAbecause it is being filtered. In this condition, the LNA typically doesnot fully compensate for the entire spectrum of noise at the SN. Toovercome this limitation, the bandwidth on the SN is lowered below thebandwidth of the column by putting the variable reset resistor in highresistance mode. The LNA is now able to compensate more fully for thenoise on the sense node.

Referring again to FIG. 6, an example pixel architecture is shown thatcan achieve both pixel reset through the optically sensitive layer andnoise reduction operations. As already described, for a more completenoise reduction operation, the reset device desirably transitionsthrough three regimes: a low resistance state, a variable highresistance, and an extremely high resistance essentially behaving likean ‘off’ state for the device. An example timing diagram for a pixeloperation sequence for this architecture is shown in FIG. 7. At the endof the Integration Phase, the Sense Node voltage will depend on theamount of charge that has been accumulated on the Sense-node electrodeSE. The reset of the Sense Node starts when the reset switch M_(RES) isclosed therefore connecting the reset electrode to the CONTROL BUS. TheCONTROL BUS is always the result of a proper operation of a columnmultiplexer (MUX) that can toggle its output between a feedbackamplifier LNA and other fixed bias voltages. At the beginning of thereset phase, the CONTROL BUS is chosen so that the optically sensitivelayer is driven in the low resistance state which will remove (flush)the charges accumulated on the Sense Node and thereby minimize or reducelag (which in imaging corresponds to image lag). This can be achievedeither via the feedback amplifier LNA or a fixed bias voltage.

After this initial phase, the feedback loop is engaged and the amplifiermodulates its output to compensate for any voltage fluctuations at theSense Node that is not filtered out by the bandwidth of the feedbackloop. In order to ensure maximum noise reduction, the bandwidth of thepixel noise fluctuations is lowered below the bandwidth of the feedbackloop (BW_(noise)<BW_(feedback)). In this implementation of the pixel,the bandwidth lowering at the Sense Node is achieved thanks to thenonlinear resistive region of the optically sensitive layer. The voltageV_(REF) can be actively modulated in this phase to provide a way toeffectively regulate/program/determine the reset operation. A sufficientinterval of time should desirably be spent in this regime to allow fullnoise reduction of all pixels and V_(REF) modulation can be used toensure this is happening. The last stage of the reset turns off theelectrical connection between the reset electrode and the sense node byfirst setting the reset electrode to a suitable potential (which is lowenough to repel charges from the reset electrode and push them towardthe Sense Node) and then turn off the reset switch M_(RES). Theintegration phase starts when the reset switch is finally turned off.

In embodiments, the capacitance of the optically sensitive layer can bereduced to increase the signal to noise ratio, as the signal to noiseratio is proportional of 1/sqrt(C). The capacitance of the opticallysensitive layer can depend on several factors. In embodiments, thecapacitance of the optically sensitive layer can be rendered lower whenthe optically sensitive layer is fully depleted of free electrons andholes at all operating potentials. The doping density required to fullydeplete the optically sensitive layer depends on the details of theoptically sensitive layer geometry and dielectric constant, as well asthe bias across the optically sensitive layer. In general, a lowerdoping density will make it easier to fully deplete. In an exampleembodiment in which the optically sensitive is a uniform thin filmapproximately 0.5 μm in thickness, and having a dielectric constant of10∈₀ (i.e., a relative dielectric constant of approximately 10), theoptically sensitive layer can be fully depleted with a greater thanabout 1 V bias across it if the doping density (either n-type or p-type)is less than approximately 1×10¹⁶ cm⁻³.

In embodiments where the doping density of the optically sensitive layeris sufficiently low such than the optically sensitive layer is fullydepleted, the capacitance of the optically sensitive layer can furtherbe reduced by the adjustment of several properties of the opticallysensitive layer. In embodiments where the optically sensitive layer is athin film of uniform thickness, the capacitance can be lower when theoptically sensitive layer is thicker. The capacitance of the opticallysensitive layer can be lower if its dielectric constant is lower. Thedielectric constant is a material property of the optically sensitivelayer depending on its chemical constituents and density.

Embodiments of the invention include a pixel circuit having a firstelectrode coupled to a reset transistor and to a first region of anoptically sensitive layer, and a second electrode coupled to a pixelsense node and to a second region of an optically sensitive layer. Theelectrical path from the first electrode, through the opticallysensitive layer, and into the second electrode functions as a variableresistor.

Embodiments include the pixel circuit where, in a first mode, thevariable resistor exhibits a resistance less than 10⁹ ohms.

Embodiments include the pixel circuit where, in a second mode, thevariable resistor exhibits a resistance exceeding 10¹⁶ ohms.

Embodiments include the pixel circuit where, in the first mode, thesense node is reset to a potential determined by the reset transistor.

Embodiments include the pixel circuit where, in the second mode, thesense node potential changes at a rate related to the optical signalilluminating the optically sensitive layer.

Embodiments include the pixel circuit where, in a third mode, the firstelectrode is electrically coupled to the output of a feedback amplifier.

Embodiments include the pixel circuit where the feedback amplifierimposes a voltage on the sense node that is specified to within a noisepower that is appreciably lesser than kT/C.

Embodiments include the pixel circuit where, in the second mode, theoptically sensitive layer is substantially fully depleted of freecarriers.

Embodiments include the pixel circuit where the optically sensitivelayer is sensitive to any one or more of the infrared, visible andultraviolet regions of the electromagnetic spectrum.

Embodiments include the pixel circuit where the optically sensitivelayer includes one or more types of quantum dot nanocrystals.

Embodiments include the pixel circuit where at least two the quantum dotnanocrystals are at least partially fused.

Embodiments include the pixel circuit where the optically sensitivelayer includes a combination at least two types of quantum dots, eachincluding a distinct semiconductor material and/or having distinctproperties.

Embodiments include the pixel circuit where the optically sensitivelayer includes an optically sensitive semiconducting polymer from thelist including {MEH-PPV, P3OT and P3HT}.

Embodiments include the pixel circuit where the optically sensitivelayer includes a polymer-quantum dot mixture having one or more types ofquantum dots sensitive to different parts of the electromagneticspectrum.

In embodiments, a pixel circuit includes a reset transistor having agate, a source, and a drain; and an optically sensitive material tocouple to a first electrode and a second electrode, with the firstelectrode being in electrical communication with the source. During afirst, hard reset interval, a residual of prior integration periods isreset, and during a second, feedback-based soft reset interval, anelectrical potential is set to a level that is defined to within a noisepower that is appreciably less than kT/C.

In embodiments, a pixel circuit includes an optically sensitive layerhaving a first electrode and a second electrode, with the firstelectrode being in electrical communication with a switch. In aintegration period mode, the switch is configured to provide a DC biasto the optically sensitive layer, and during a feedback-reset periodmode, the switch is configured to couple to a feedback reset device. Thefeedback reset device is configured to impose a reset to a defined resetvoltage level that is specified to within a noise power that isappreciably less than kT/C.

Referring now to FIG. 11, additional example embodiments provide imagesensing regions that use an array of pixel elements to detect an image.The pixel elements may include photosensitive material. The image sensormay detect a signal from the photosensitive material in each of thepixel regions that varies based on the intensity of light incident onthe photosensitive material. In one example embodiment, thephotosensitive material is a continuous film of interconnectednanoparticles. Electrodes are used to apply a bias across each pixelarea. Pixel circuitry is used to integrate a signal in a charge storeover a period of time for each pixel region. The circuit stores anelectrical signal proportional to the intensity of light incident on theoptically sensitive layer during the integration period. The electricalsignal can then be read from the pixel circuitry and processed toconstruct a digital image corresponding to the light incident on thearray of pixel elements. In example embodiments, the pixel circuitry maybe formed on an integrated circuit device below the photosensitivematerial. For example, a nanocrystal photosensitive material may belayered over a CMOS integrated circuit device to form an image sensor.Metal contact layers from the CMOS integrated circuit may beelectrically connected to the electrodes that provide a bias across thepixel regions. U.S. patent application Ser. No. 12/10,625, titled“Materials, Systems and Methods for Optoelectronic Devices,” filed Apr.18, 2008 (Publication No. 2009/0152664) includes additional descriptionsof optoelectronic devices, systems and materials that may be used inconnection with example embodiments and is hereby incorporated herein byreference in its entirety. This is an example embodiment only and otherembodiments may use different photodetectors and photosensitivematerials. For example, embodiments may use silicon or Gallium Arsenide(GaAs) photo detectors.

Image sensors incorporate arrays of photodetectors. These photodetectorssense light, converting it from an optical to an electronic signal. FIG.11 shows structure of and areas relating to quantum dot pixel chipstructures (QDPCs) 100, according to example embodiments. As illustratedin FIG. 11, the QDPC 100 may be adapted as a radiation 1000 receiverwhere quantum dot structures 1100 are presented to receive the radiation1000, such as light. The QDPC 100 includes, as will be described in moredetail herein, quantum dot pixels 1800 and a chip 2000 where the chip isadapted to process electrical signals received from the quantum dotpixel 1800. The quantum dot pixel 1800 includes the quantum dotstructures 1100 include several components and sub components such asquantum dots 1200, quantum dot materials 200 and particularconfigurations or quantum dot layouts 300 related to the dots 1200 andmaterials 200. The quantum dot structures 1100 may be used to createphotodetector structures 1400 where the quantum dot structures areassociated with electrical interconnections 1404. The electricalconnections 1404 are provided to receive electric signals from thequantum dot structures and communicate the electric signals on to pixelcircuitry 1700 associated with pixel structures 1500.

Just as the quantum dot structures 1100 may be laid out in variouspatterns, both planar and vertical, the photodetector structures 1400may have particular photodetector geometric layouts 1402. Thephotodetector structures 1400 may be associated with pixel structures1500 where the electrical interconnections 1404 of the photodetectorstructures are electrically associated with pixel circuitry 1700. Thepixel structures 1500 may also be laid out in pixel layouts 1600including vertical and planar layouts on a chip 2000 and the pixelcircuitry 1700 may be associated with other components 1900, includingmemory for example. The pixel circuitry 1700 may include passive andactive components for processing of signals at the pixel 1800 level. Thepixel 1800 is associated both mechanically and electrically with thechip 2000. In example embodiments, the pixel structures 1500 and pixelcircuitry 1700 include structures and circuitry for film binning and/orcircuit binning of separate color elements for multiple pixels asdescribed herein. From an electrical viewpoint, the pixel circuitry 1700may be in communication with other electronics (e.g., chip processor2008). The other electronics may be adapted to process digital signals,analog signals, mixed signals and the like and it may be adapted toprocess and manipulate the signals received from the pixel circuitry1700. In other embodiments, a chip processor 2008 or other electronicsmay be included on the same semiconductor substrate as the QDPCs and maybe structured using a system-on-chip architecture. The other electronicsmay include circuitry or software to provide digital binning in exampleembodiments. The chip 2000 also includes physical structures 2002 andother functional components 2004, which will also be described in moredetail below.

The QDPC 100 detects electromagnetic radiation 1000, which inembodiments may be any frequency of radiation from the electromagneticspectrum. Although the electromagnetic spectrum is continuous, it iscommon to refer to ranges of frequencies as bands within the entireelectromagnetic spectrum, such as the radio band, microwave band,infrared band (IR), visible band (VIS), ultraviolet band (UV), X-rays,gamma rays, and the like. The QDPC 100 may be capable of sensing anyfrequency within the entire electromagnetic spectrum; however,embodiments herein may reference certain bands or combinations of bandswithin the electromagnetic spectrum. It should be understood that theuse of these bands in discussion is not meant to limit the range offrequencies that the QDPC 100 may sense, and are only used as examples.Additionally, some bands have common usage sub-bands, such as nearinfrared (NIR) and far infrared (FIR), and the use of the broader bandterm, such as IR, is not meant to limit the QDPCs 100 sensitivity to anyband or sub-band. Additionally, in the following description, terms suchas “electromagnetic radiation,” “radiation,” “electromagnetic spectrum,”“spectrum,” “radiation spectrum,” and the like are used interchangeably,and the term color is used to depict a select band of radiation 1000that could be within any portion of the radiation 1000 spectrum, and isnot meant to be limited to any specific range of radiation 1000 such asin visible ‘color’.

In the example embodiment of FIG. 11, the nanocrystal materials andphotodetector structures described above may be used to provide quantumdot pixels 1800 for a photosensor array, image sensor or otheroptoelectronic device. In example embodiments, the pixels 1800 includequantum dot structures 1100 capable of receiving radiation 1000,photodetectors structures adapted to receive energy from the quantum dotstructures 1100 and pixel structures. The quantum dot pixels describedherein can be used to provide the following in some embodiments: highfill factor, color binning, potential to stack, potential to go to smallpixel sizes, high performance from larger pixel sizes, simplify colorfilter array, elimination of de-mosaicing, self-gain setting/automaticgain control, high dynamic range, global shutter capability,auto-exposure, local contrast, speed of readout, low noise readout atpixel level, ability to use larger process geometries (lower cost),ability to use generic fabrication processes, use digital fabricationprocesses to build analog circuits, adding other functions below thepixel such as memory, A to D, true correlated double sampling, binning,etc. Example embodiments may provide some or all of these features.However, some embodiments may not use these features.

A quantum dot 1200 may be a nanostructure, typically a semiconductornanostructure that confines a conduction band electrons, valence bandholes, or excitons (bound pairs of conduction band electrons and valenceband holes) in all three spatial directions. A quantum dot exhibits inits absorption spectrum the effects of the discrete quantized energyspectrum of an idealized zero-dimensional system. The wave functionsthat correspond to this discrete energy spectrum are typicallysubstantially spatially localized within the quantum dot, but extendover many periods of the crystal lattice of the material.

FIG. 12 shows an example of a quantum dot 1200. In one exampleembodiment, the QD 1200 has a core 1220 of a semiconductor or compoundsemiconductor material, such as PbS. Ligands 1225 may be attached tosome or all of the outer surface or may be removed in some embodimentsas described further below. In some embodiments, the cores 1220 ofadjacent QDs may be fused together to form a continuous film ofnanocrystal material with nanoscale features. In other embodiments,cores may be connected to one another by linker molecules.

Some embodiments of the QD optical devices are single image sensor chipsthat have a plurality of pixels, each of which includes a QD layer thatis radiation 1000 sensitive, e.g., optically active, and at least twoelectrodes in electrical communication with the QD layer. The currentand/or voltage between the electrodes is related to the amount ofradiation 1000 received by the QD layer. Specifically, photons absorbedby the QD layer generate electron-hole pairs, such that, if anelectrical bias is applied, a current flows. By determining the currentand/or voltage for each pixel, the image across the chip can bereconstructed. The image sensor chips have a high sensitivity, which canbe beneficial in low-radiation-detecting 1000 applications; a widedynamic range allowing for excellent image detail; and a small pixelsize. The responsivity of the sensor chips to different opticalwavelengths is also tunable by changing the size of the QDs in thedevice, by taking advantage of the quantum size effects in QDs. Thepixels can be made as small as 1 square micron or less, or as large as30 microns by 30 microns or more or any range subsumed therein.

The photodetector structure 1400 of FIGS. 11 and 13 shows a deviceconfigured so that it can be used to detect radiation 1000 in exampleembodiments. The detector may be ‘tuned’ to detect prescribedwavelengths of radiation 1000 through the types of quantum dotstructures 1100 that are used in the photodetector structure 1400. Thephotodetector structure can be described as a quantum dot structure 1100with an I/O for some input/output ability imposed to access the quantumdot structures' 1100 state. Once the state can be read, the state can becommunicated to pixel circuitry 1700 through an electricalinterconnection 1404, wherein the pixel circuitry may includeelectronics (e.g., passive and/or active) to read the state. In anembodiment, the photodetector structure 1400 may be a quantum dotstructure 1100 (e.g., film) plus electrical contact pads so the pads canbe associated with electronics to read the state of the associatedquantum dot structure.

In embodiments, processing may include binning of pixels in order toreduce random noise associated with inherent properties of the quantumdot structure 1100 or with readout processes. Binning may involve thecombining of pixels 1800, such as creating 2×2, 3×3, 5×5, or the likesuperpixels. There may be a reduction of noise associated with combiningpixels 1800, or binning, because the random noise increases by thesquare root as area increases linearly, thus decreasing the noise orincreasing the effective sensitivity. With the QDPC's 100 potential forvery small pixels, binning may be utilized without the need to sacrificespatial resolution, that is, the pixels may be so small to begin withthat combining pixels doesn't decrease the required spatial resolutionof the system. Binning may also be effective in increasing the speedwith which the detector can be run, thus improving some feature of thesystem, such as focus or exposure. In example embodiments, binning maybe used to combine subpixel elements for the same color or range ofradiation (including UV and/or IR) to provide separate elements for asuperpixel while preserving color/UV/IR resolution as further describedbelow.

In embodiments the chip may have functional components that enablehigh-speed readout capabilities, which may facilitate the readout oflarge arrays, such as 5 Mpixels, 6 Mpixels, 8 Mpixels, 12 Mpixels, orthe like. Faster readout capabilities may require more complex, largertransistor-count circuitry under the pixel 1800 array, increased numberof layers, increased number of electrical interconnects, widerinterconnection traces, and the like.

In embodiments, it may be desirable to scale down the image sensor sizein order to lower total chip cost, which may be proportional to chiparea. However, shrinking chip size may mean, for a given number ofpixels, smaller pixels. In existing approaches, since radiation 1000must propagate through the interconnect layer onto the monolithicallyintegrated silicon photodiode lying beneath, there is a fill-factorcompromise, whereby part of the underlying silicon area is obscured byinterconnect; and, similarly, part of the silicon area is consumed bytransistors used in read-out. One workaround is micro-lenses, which addcost and lead to a dependence in photodiode illumination on positionwithin the chip (center vs. edges); another workaround is to go tosmaller process geometries, which is costly and particularly challengingwithin the image sensor process with its custom implants.

In embodiments, the technology discussed herein may provide a way aroundthese compromises. Pixel size, and thus chip size, may be scaled downwithout decreasing fill factor. Larger process geometries may be usedbecause transistor size, and interconnect line-width, may not obscurepixels since the photodetectors are on the top surface, residing abovethe interconnect. In the technology proposed herein, large geometriessuch as 0.13 μm and 0.18 μm may be employed without obscuring pixels.Similarly, small geometries such as 90 nm and below may also beemployed, and these may be standard, rather thanimage-sensor-customized, processes, leading to lower cost. The use ofsmall geometries may be more compatible with high-speed digital signalprocessing on the same chip. This may lead to faster, cheaper, and/orhigher-quality image sensor processing on chip. Also, the use of moreadvanced geometries for digital signal processing may contribute tolower power consumption for a given degree of image sensor processingfunctionality.

An example integrated circuit system that can be used in combinationwith the above photodetectors, pixel regions and pixel circuits will nowbe described in connection with FIG. 15. FIG. 15 is a block diagram ofan image sensor integrated circuit (also referred to as an image sensorchip). The chip is shown to include:

-   -   a pixel array (100) in which incident light is converted into        electronic signals, and in which electronic signals are        integrated into charge stores whose contents and voltage levels        are related to the integrated light incident over the frame        period; the pixel array may include color filters and electrode        structures for color film binning as described further below;    -   row and column circuits (110 and 120) which are used to reset        each pixel, and read the signal related to the contents of each        charge store, in order to convey the information related to the        integrated light over each pixel over the frame period to the        outer periphery of the chip; the pixel circuitry may include        circuitry for color binning as described further below;    -   analog circuits (130, 140, 150, 160, 230). The pixel electrical        signal from the column circuits is fed into the        analog-to-digital convert (160) where it is converted into a        digital number representing the light level at each pixel. The        pixel array and ADC are supported by analog circuits that        provide bias and reference levels (130, 140, & 150).    -   digital circuits (170, 180, 190, 200). The Image Enhancement        circuitry (170) provides image enhancement functions to the data        output from ADC to improve the signal to noise ratio. Line        buffer (180) temporarily stores several lines of the pixel        values to facilitate digital image processing and IO        functionality. (190) is a bank of registers that prescribe the        global operation of the system and/or the frame format. Block        200 controls the operation of the chip. The digital circuits may        also include circuits or software for digital color binning;    -   IO circuits (210 & 220) support both parallel input/output and        serial input/output. (210) is a parallel IO interface that        outputs every bit of a pixel value simultaneously. (220) is a        serial IO interface where every bit of a pixel value is output        sequentially; and    -   a phase-locked loop (230) provides a clock to the whole chip.

In a particular example embodiment, when 0.11 μm CMOS technology node isemployed, the periodic repeat distance of pixels along the row-axis andalong the column-axis may be 900 nm, 1.1 μm, 1.2 μm, 1.4 μm, 1.75 μm,2.2 μm, or larger. The implementation of the smallest of these pixelssizes, especially 900 nm, 1.1 μm, and 1.2 μm, may require transistorsharing among pairs or larger group of adjacent pixels in someembodiments.

Very small pixels can be implemented in part because all of the siliconcircuit area associated with each pixel can be used for read-outelectronics since the optical sensing function is achieved separately,in another vertical level, by the optically-sensitive layer that residesabove the interconnect layer.

Because the optically sensitive layer and the read-out circuit thatreads a particular region of optically sensitive material exist onseparate planes in the integrated circuit, the shape (viewed from thetop) of (1) the pixel read-out circuit and (2) the optically sensitiveregion that is read by (1); can be generally different. For example itmay be desired to define an optically sensitive region corresponding toa pixel as a square; whereas the corresponding read-out circuit may bemost efficiently configured as a rectangle.

In an imaging array based on a top optically sensitive layer connectedthrough vias to the read-out circuit beneath, there exists no imperativefor the various layers of metal, vias, and interconnect dielectric to besubstantially or even partially optically transparent, although they maybe transparent in some embodiments. This contrasts with the case offront-side-illuminated CMOS image sensors in which a substantiallytransparent optical path must exist traversing the interconnect stack.

Pixel circuitry may be defined to include components beginning at theelectrodes in contact with the quantum dot material 200 and ending whensignals or information is transferred from the pixel to other processingfacilities, such as the functional components 2004 of the underlyingchip 200 or another quantum dot pixel 1800. Beginning at the electrodeson the quantum dot material 200, the signal is translated or read. Inembodiments, the quantum dot material 200 may provide a change incurrent flow in response to radiation 1000. The quantum dot pixel 1800may require bias circuitry 1700 in order to produce a readable signal.This signal in turn may then be amplified and selected for readout.

One embodiment of a pixel circuit shown in FIG. 14 uses a reset-biastransistor 1802, amplifier transistor 1804, and column addresstransistor 1808. This three-transistor circuit configuration may also bereferred to as a 3T circuit. Here, the reset-bias transistor 1802connects the bias voltage 1702 to the photoconductive photovoltaicquantum dot material 200 when reset 1704 is asserted, thus resetting theelectrical state of the quantum dot material 200. After reset 1704, thequantum dot material 200 may be exposed to radiation 1000, resulting ina change in the electrical state of the quantum dot material 200, inthis instance a change in voltage leading into the gate of the amplifier1804. This voltage is then boosted by the amplifier transistor 1804 andpresented to the address selection transistor 1808, which then appearsat the column output of the address selection transistor 1808 whenselected. In some embodiments, additional circuitry may be added to thepixel circuit to help subtract out dark signal contributions. In otherembodiments, adjustments for dark signal can be made after the signal isread out of the pixel circuit. In example, embodiments, additionalcircuitry may be added for film binning or circuit binning.

FIG. 16 shows an embodiment of a single-plane computing device 100 thatmay be used in computing, communication, gaming, interfacing, and so on.The single-plane computing device 100 is shown to include a peripheralregion 101 and a display region 103. A touch-based interface device 117,such as a button or touchpad, may be used in interacting with thesingle-plane computing device 100.

An example of a first camera module 113 is shown to be situated withinthe peripheral region 101 of the single-plane computing device 100 andis described in further detail, below. Example light sensors 115A, 115Bare also shown to be situated within the peripheral region 101 of thesingle-plane computing device 100 and are described in further detail,below, with reference to FIG. 19. An example of a second camera module105 is shown to be situated in the display region 103 of thesingle-plane computing device 100 and is described in further detail,below, with reference to FIG. 18.

Examples of light sensors 107A, 107B, shown to be situated in thedisplay region 103 of the single-plane computing device 100 and aredescribed in further detail, below, with reference to FIG. 19. Anexample of a first source of optical illumination 111 (which may bestructured or unstructured) is shown to be situated within theperipheral region 101 of the single-plane computing device 100. Anexample of a second source of optical illumination 109 is shown to besituated in the display region 103.

In embodiments, the display region 103 may be a touchscreen display. Inembodiments, the single-plane computing device 100 may be a tabletcomputer. In embodiments, the single-plane computing device 100 may be amobile handset.

FIG. 17 shows an embodiment of a double-plane computing device 200 thatmay be used in computing, communication, gaming, interfacing, and so on.The double-plane computing device 200 is shown to include a firstperipheral region 201A and a first display region 203A of a first plane210, a second peripheral region 201B and a second display region 203B ofa second plane 230, a first touch-based interface device 217A of thefirst plane 210 and a second touch-based interface device 217B of thesecond plane 230. The example touch-based interface devices 217A, 217Bmay be buttons or touchpads that may be used in interacting with thedouble-plane computing device 200. The second display region 203B mayalso be an input region in various embodiments.

The double-plane computing device 200 is also shown to include examplesof a first camera module 213A in the first peripheral region 201A and asecond camera module 213B in the second peripheral region 201B. Thecamera modules 213A, 213B are described in more detail, below, withreference to FIG. 18. As shown, the camera modules 213A, 213B aresituated within the peripheral regions 201A, 201B of the double-planecomputing device 200. Although a total of two camera modules are shown,a person of ordinary skill in the art will recognize that more or fewerlight sensors may be employed.

A number of examples of light sensors 215A, 215B, 215C, 215D, are shownsituated within the peripheral regions 201A, 201B of the double-planecomputing device 200. Although a total of four light sensors are shown,a person of ordinary skill in the art will recognize that more or fewerlight sensors may be employed. Examples of the light sensors 215A, 215B,215C, 215D, are described, below, in further detail with reference toFIG. 18. As shown, the light sensors 215A, 215B, 215C, 215D, aresituated within the peripheral regions 201A, 201B of the double-planecomputing device 200.

The double-plane computing device 200 is also shown to include examplesof a first camera module 205A in the first display region 203A and asecond camera module 205B in the second display region 203B. The cameramodules 205A, 205B are described in more detail, below, with referenceto FIG. 18. As shown, the camera modules 205A, 205B are situated withinthe display regions 203A, 203B of the double-plane computing device 200.Also shown as being situated within the display regions 203A, 203B ofthe double-plane computing device 200 are examples of light sensors207A, 207B, 207C, 207D. Although a total of four light sensors areshown, a person of ordinary skill in the art will recognize that more orfewer light sensors may be employed. Examples of the light sensors 207A,207B, 207C, 207D are described, below, in further detail with referenceto FIG. 19. Example sources of optical illumination 211A, 211B are shownsituated within the peripheral region 201A, 201B and other examplesources of optical illumination 209A, 209B are shown situated within oneof the display regions 203A, 203B and are also described with referenceto FIG. 19, below. A person of ordinary skill in the art will recognizethat various numbers and locations of the described elements, other thanthose shown or described, may be implemented.

In embodiments, the double-plane computing device 200 may be a laptopcomputer. In embodiments, the double-plane computing device 200 may be amobile handset.

With reference now to FIG. 18, an embodiment of a camera module 300 thatmay be used with the computing devices of FIG. 16 or FIG. 17 is shown.The camera module 300 may correspond to the camera module 113 of FIG. 16or the camera modules 213A, 213B of FIG. 17. As shown in FIG. 18, thecamera module 300 includes a substrate 301, an image sensor 303, andbond wires 305. A holder 307 is positioned above the substrate. Anoptical filter 309 is shown mounted to a portion of the holder 307. Abarrel 311 holds a lens 313 or a system of lenses.

FIG. 19 shows an embodiment of a light sensor 400 that may be used withthe computing devices of FIG. 16 or FIG. 17 an example embodiment of alight sensor. The light sensor 400 may correspond to the light sensors115A, 115B of FIG. 16 of the light sensors 215A, 215B, 215C, 215D ofFIG. 17. The light sensor 400 is shown to include a substrate 401, whichmay correspond to a portion of either or both of the peripheral region101 or the display region 103 of FIG. 16. The substrate 401 may alsocorrespond to a portion of either or both of the peripheral regions201A, 201B or the display regions 203A, 203B of FIG. 17. The lightsensor 400 is also shown to include electrodes 403A, 403B used toprovide a bias across light-absorbing material 405 and to collectphotoelectrons therefrom. An encapsulation material 407 or a stack ofencapsulation materials is shown over the light-absorbing material 405.Optionally, the encapsulation material 407 may include conductiveencapsulation material for biasing and/or collecting photoelectrons fromthe light-absorbing material 405.

Elements of a either the single-plane computing device 100 of FIG. 16,or the double-plane computing device 200 of FIG. 17, may be connected orotherwise coupled with one another. Embodiments of the computing devicesmay include a processor. It may include functional blocks, and/orphysically distinct components, that achieve computing, imageprocessing, digital signal processing, storage of data, communication ofdata (through wired or wireless connections), the provision of power todevices, and control of devices. Devices that are in communication withthe processor include devices of FIG. 16 may include the display region103, the touch-based interface device 117, the camera modules 105, 113,the light sensors 115A, 115B, 107A, 107B, and the sources of opticalillumination 109, 111. Similarly correspondences may apply to FIG. 17 aswell.

The light sensor of FIG. 19 may include a light-absorbing material 405of various designs and compositions. In embodiments, the light-absorbingmaterial may be designed to have an absorbance that is sufficientlysmall, across the visible wavelength region approximately 450 nm to 650nm, such that, in cases in which the light sensor of FIG. 19 isincorporated into the display region of a computing device, only amodest fraction of visible light incident upon the sensor is absorbed bythe light-absorbing material. In this case, the quality of the imagesdisplayed using the display region is not substantially compromised bythe incorporation of the light-absorbing material along the optical pathof the display. In embodiments, the light-absorbing material 405 mayabsorb less than 30%, or less than 20%, or less than 10%, of lightimpinging upon it in across the visible spectral region.

In embodiments, the electrodes 403A, 403B, and, in the case of aconductive encapsulant for 407, the top electrode 407, may beconstituted using materials that are substantially transparent acrossthe visible wavelength region approximately 450 nm to 650 nm. In thiscase, the quality of the images displayed using the display region isnot substantially compromised by the incorporation of thelight-absorbing material along the optical path of the display.

In embodiments, the light sensor of FIG. 19 may include a light-sensingmaterial capable of sensing infrared light. In embodiments, thelight-sensing material may be a semiconductor having a bandgapcorresponding to an infrared energy, such as in the range 0.5 eV-1.9 eV.In embodiments, the light-sensing material may have measurableabsorption in the infrared spectral range; and may have measurableabsorption also in the visible range. In embodiments, the light-sensingmaterial may absorb a higher absorbance in the visible spectral range asin the infrared spectral range; yet may nevertheless be used to sensegesture-related signals in the infrared spectral range.

In an example embodiment, the absorbance of the light-sensingdisplay-incorporated material may lie in the range 2-20% in the visible;and may lie in the range 0.1-5% in the infrared. In an exampleembodiment, the presence of visible light in the ambient, and/or emittedfrom the display, may produce a background signal within the lightsensor, as a consequence of the material visible-wavelength absorptionwithin the light-absorbing material of the light sensor. In an exampleembodiment, sensing in the infrared region may also be achieved. Thelight sources used in aid of gesture recognition may be modulated usingspatial, or temporal, codes, allowing them to be distinguished from thevisible-wavelength-related component of the signal observed in the lightsensor. In an example embodiment, at least one light source used in aidof gesture recognition may be modulated in time using a code having afrequency component greater than 100 Hz, 1000 Hz, 10 kHz, or 100 kHz. Inan example embodiment, the light sensor may have a temporal responsehaving a cutoff frequency greater than said frequency components. Inembodiments, circuitry may be employed to ensure that the frequencycomponent corresponding to gesture recognition can be extracted andmonitored, with the background components related to the room ambient,the display illumination, and other such non-gesture-related backgroundinformation substantially removed. In this example, the light sensors,even though they absorb both visible and infrared light, can provide asignal that is primarily related to gestural information of interest ingesture recognition.

In an example embodiment, an optical source having a total optical powerof approximately 1 mW may be employed. When illuminating an object adistance approximately 10 cm away, where the object has areaapproximately 1 cm2 and diffuse reflectance approximately 20%, then theamount of power incident on a light sensor having area 1 cm2 may be oforder 100 pW. In an example embodiment, a light sensor having absorbanceof 1% may be employed, corresponding to a photocurrent related to thelight received as a consequence of the illumination via the opticalsource, and reflected or scattered off of the object, and thus incidentonto the light sensor, may therefore be of order pW. In exampleembodiments, the electrical signal reported by the light sensor maycorrespond to approximately pA signal component at the modulationfrequency of the optical source. In example embodiments, a largeadditional signal component, such as in the nA or μA range, may arisedue to visible and infrared background, display light, etc. In exampleembodiments, the relatively small signal components, with itsdistinctive temporal and/or spatial signature as provided by modulation(in time and/or space) of the illumination source, may nevertheless beisolated relative to other background/signal, and may be employed todiscern gestural information.

In embodiments, light-absorbing material 405 may consist of a materialthat principally absorbs infrared light in a certain band; and that issubstantially transparent to visible-wavelength light. In an exampleembodiment, a material such as PBDTT-DPP, the near-infraredlight-sensitive polymerpoly(2,60-4,8-bis(5-ethylhexylthienyl)benzo-[1,2-b;3,4-b]dithiophene-alt-5-dibutyloctyl-3,6-bis(5-bromothiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4-dione),may be employed as a component of the light-absorbing layer.

In embodiments, the electronic signal produced by the light sensor maybe communicated to a device for electronic amplification. This devicemay amplify a specific electronic frequency band more than other bands,producing an enhanced signal component that is related to the gesturalinformation. The signal from the light sensor, possibly with thecombination of amplification (potentially frequency-dependent), may beinput to an analog-to-digital converter that can produce a digitalsignal related to the gestural information. The digital informationrelated to gestural information can be further conveyed to otherintegrated circuits and/or signal processing engines in the context of asystem. For example, it may be conveyed to an application processor.

In embodiments, optical sources used to illuminate a volume of space,with the goal of enabling gesture recognition, may use illumination at anear infrared wavelength that is substantially unseen by the human eye.In an example embodiment, a light-emitting diode having centerwavelength of approximately 950 nm may be employed.

In embodiments, gesture recognition may be accomplished by combininginformation from at least one camera, embedded into the computingdevice, and having a lens providing a substantially focused image ontoan image sensor that is part of the camera; and may also incorporatesensors in the peripheral region, and/or integrated into the displayregion. In embodiments, the distributed sensors may provide generalinformation on the spatio-temporal movements of the object being imaged;and the signals from the at least one camera(s) may be combined with thedistributed sensors' signals to provide a morespatially-/temporally-accurate picture of the two- or three-dimensionalmotion of the object whose gesture is to be recognized. In an exampleembodiment, the camera may employ an image sensor providing a modestspatial resolution, such as QVGA, VGA, SVGA, etc., and thus beimplemented using an image sensor having small die size and thus lowcost; and also be implemented using a camera module having small x, y,and z form factor, enabling minimal consumption of peripheral regionarea, and no substantial addition to the z-height of the tablet or othercomputing device.

In embodiments, a moderate frame rate, such as 15 fps, 30 fps, or 60 fpsmay be employed, which, combined with a modest resolution, enables alow-cost digital communication channel and moderate complexity of signalprocessing in the recognition of gestures. In embodiments, the at leastone camera module may implement wide field of view imaging in order toprovide a wide angular range in the assessment of gestures in relationto a display. In embodiments, at least one camera module may be tilted,having its angle of regard nonparallel to the normal direction(perpendicular direction) to the display, enabling the at least onecamera to image an angular extent in closer proximity to the display.

In embodiments, multiple cameras may be employed in combination, eachhaving an angle of regard distinct from at least one another, therebyenabling gestures in moderate proximity to the display to be imaged andinterpreted. In embodiments, the at least one camera may employ an imagesensor sensitized using light-detecting materials that provide highquantum efficiency, for example, greater than 30%, at near infraredwavelength used by the illuminating source; this enables reducedrequirement for power and/or intensity in the illuminating source. Inembodiments, the illuminating source may be modulated in time at aspecific frequency and employing a specific temporal pattern (e.g., aseries of pulses of known spacing and width in time); and the signalfrom the at least one camera and/or the at least one distributed sensormay be interpreted with knowledge of the phase and temporal profile ofthe illuminating source; and in this manner, increased signal-to-noiseratio, akin to lock-in or boxcar-averaging or other filtering and/oranalog or digital signal processing methods, may be used tosubstantially pinpoint the modulated, hence illuminated signal, andsubstantially remove or minimize the background signal associated withthe background scene.

FIG. 20 shows an embodiment of a method of gesture recognition. Themethod comprises an operation 501 that includes acquiring a stream intime of at least two images from each of at least one of the cameramodule(s); and an operation 507 that includes also acquiring a stream,in time, of at least two signals from each of at least one of the lightsensors. The method further comprises, at operations 503 and 509,conveying the images and/or signals to a processor. The method furthercomprises, at operation 505, using the processor, an estimate of agesture's meaning, and timing, based on the combination of the imagesand signals.

FIG. 21 shows an embodiment of a method of gesture recognition. Themethod comprises an operation 601 that includes acquiring a stream intime of at least two images from each of at least one of the cameramodules; and an operation 607 that includes also acquiring a stream, intime, of at least two signals from each of at least one of thetouch-based interface devices. The method further comprises, atoperations 603 and 609, conveying the images and/or signals to aprocessor. The method further comprises, at operation 605, using theprocessor, an estimate of a gesture's meaning, and timing, based on thecombination of the images and signals.

In embodiments, signals received by at least one of (1) the touch-basedinterface devices; (2) the camera modules; (3) the light sensors, eachof these either within the peripheral and/or the display ordisplay/input regions, may be employed and, singly or jointly, used todetermine the presence, and the type, of gesture indicated by a user ofthe device.

Referring again to FIG. 20, in embodiments, a stream, in time, of imagesis acquired from each of at least one of the camera modules. A stream,in time, of at least two signals from each of at least one of the lightsensors is also acquired. In embodiments, the streams may be acquiredfrom the different classes of peripheral devices synchronously. Inembodiments, the streams may be acquired with known time stampsindicating when each was acquired relative to the others, for example,to some conference reference time point. In embodiments, the streams areconveyed to a processor. The processor computes an estimate of thegesture's meaning, and timing, based on the combination of the imagesand signals.

In embodiments, at least one camera module has a wide field of viewexceeding about 40°. In embodiments, at least one camera module employsa fisheye lens. In embodiments, at least one image sensor achieveshigher resolution at its center, and lower resolution in its periphery.In embodiments, at least one image sensor uses smaller pixels near itscenter and larger pixels near its periphery.

In embodiments, active illumination via at least one light source;combined with partial reflection and/or partial scattering off of aproximate object; combined with light sensing using at least one opticalmodule or light sensor; may be combined to detect proximity to anobject. In embodiments, information regarding such proximity may be usedto reduce power consumption of the device. In embodiments, powerconsumption may be reduced by dimming, or turning off, power-consumingcomponents such as a display.

In embodiments, at least one optical source may emit infrared light. Inembodiments, at least one optical source may emit infrared light in thenear infrared between about 700 nm and about 1100 nm. In embodiments, atleast one optical source may emit infrared light in the short-wavelengthinfrared between about 1100 nm and about 1700 nm wavelength. Inembodiments, the light emitted by the optical source is substantiallynot visible to the user of the device.

In embodiments, at least one optical source may project a structuredlight image. In embodiments, spatial patterned illumination, combinedwith imaging, may be employed to estimate the relative distance ofobjects relative to the imaging system.

In embodiments, at least two lensing systems may be employed to image ascene, or portions of a scene, onto two distinct regions of amonolithically-integrated single image sensor integrated circuit; andthe patterns of light thus acquired using the image sensor integratedcircuit may be used to aid in estimating the relative or absolutedistances of objects relative to the image sensor system.

In embodiments, at least two lensing systems may be employed to image ascene, or portions of a scene, onto two distinct image sensor integratedcircuits housed within a single camera system; and the patterns of lightthus acquired using the image sensor integrated circuits may be used toaid in estimating the relative or absolute distances of objects relativeto the image sensor system.

In embodiments, at least two lensing systems may be employed to image ascene, or portions of a scene, onto two distinct image sensor integratedcircuits housed within separate camera systems or subsystems; and thepatterns of light thus acquired using the image sensor integratedcircuits may be used to aid in estimating the relative or absolutedistances of objects relative to the image sensor systems or subsystems.

In embodiments, the different angles of regard, or perspectives, fromwhich the at least two optical systems perceive the scene, may be usedto aid in estimating the relative or absolute distances of objectsrelative to the image sensor system.

In embodiments, light sensors such as the light sensors 115A, 115Bsituated in the peripheral region 101 of FIG. 16, and/or the lightsensors 107A, 107B situated in the display region 103 of FIG. 16, may beused singly, or in combination with one another, and/or in combinationwith camera modules, to acquire information about a scene. Inembodiments, light sensors may employ lenses to aid in directing lightfrom certain regions of a scene onto specific light sensors. Inembodiments, light sensors may employ systems for aperturing, such aslight-blocking housings, that define a limited angular range over whichlight from a scene will impinge on a certain light sensor. Inembodiments, a specific light sensor will, with the aid of aperturing,be responsible for sensing light from within a specific angular cone ofincidence.

In embodiments, the different angles of regard, or perspectives, fromwhich the at least two optical systems perceive the scene, may be usedto aid in estimating the relative or absolute distances of objectsrelative to the image sensor system.

In embodiments, the time sequence of light detector from at least twolight sensors may be used to estimate the direction and velocity of anobject. In embodiments, the time sequence of light detector from atleast two light sensors may be used to ascertain that a gesture was madeby a user of a computing device. In embodiments, the time sequence oflight detector from at least two light sensors may be used to classifythe gesture that was made by a user of a computing device. Inembodiments, information regarding the classification of a gesture, aswell as the estimated occurrence in time of the classified gesture, maybe conveyed to other systems or subsystems within a computing device,including to a processing unit.

In embodiments, light sensors may be integrated into the display regionof a computing device, for example, the light sensors 107A, 107B of FIG.16. In embodiments, the incorporation of the light sensors into thedisplay region can be achieved without the operation of the display inthe conveyance of visual information to the user being substantiallyaltered. In embodiments, the display may convey visual information tothe user principally using visible wavelengths in the range of about 400nm to about 650 nm, while the light sensors may acquire visualinformation regarding the scene principally using infrared light ofwavelengths longer than about 650 nm. In embodiments, a ‘display plane’operating principally in the visible wavelength region may reside infront of—closer to the user—than a ‘light sensing plane’ that mayoperate principally in the infrared spectral region.

In embodiments, structured light of a first type may be employed, and ofa second type may also be employed, and the information from the atleast two structured light illuminations may be usefully combined toascertain information regarding a scene that exceeds the informationcontained in either isolated structured light image.

In embodiments, structured light of a first type may be employed toilluminate a scene and may be presented from a first source providing afirst angle of illumination; and structured light of a second type maybe employed to illuminate a scene and may be presented from a secondsource providing a second angle of illumination.

In embodiments, structured light of a first type and a first angle ofillumination may be sensed using a first image sensor providing a firstangle of sensing; and also using a second image sensor providing asecond angle of sensing.

In embodiments, structured light having a first pattern may be presentedfrom a first source; and structured light having a second pattern may bepresented from a second source.

In embodiments, structured light having a first pattern may be presentedfrom a source during a first time period; and structured light having asecond pattern may be presented from a source during a second timeperiod.

In embodiments, structured light of a first wavelength may be used toilluminate a scene from a first source having a first angle ofillumination; and structured light of a second wavelength may be used toilluminate a scene from a second source having a second angle ofillumination.

In embodiments, structured light of a first wavelength may be used toilluminate a scene using a first pattern; and structured light of asecond wavelength may be used to illuminate a scene using a secondpattern. In embodiments, a first image sensor may sense the scene with astrong response at the first wavelength and a weak response at thesecond wavelength; and a second image sensor may sense the scene with astrong response at the second wavelength and a weak response at thefirst wavelength. In embodiments, an image sensor may consist of a firstclass of pixels having strong response at the first wavelength and weakresponse at the second wavelength; and of a second class of pixelshaving strong response at the second wavelength and weak response at thefirst wavelength.

Embodiments include image sensor systems that employ a filter having afirst bandpass spectral region; a first bandblock spectral region; and asecond bandpass spectral region. Embodiments include the first bandpassregion corresponding to the visible spectral region; the first bandblockspectral region corresponding to a first portion of the infrared; andthe second bandpass spectral region corresponding to a second portion ofthe infrared. Embodiments include using a first time period to detectprimarily the visible-wavelength scene; and using active illuminationwithin the second bandpass region during a second time period to detectthe sum of a visible-wavelength scene and an actively-illuminatedinfrared scene; and using the difference between images acquired duringthe two time periods to infer a primarily actively-illuminated infraredscene. Embodiments include using structured light during the second timeperiod. Embodiments include using infrared structured light. Embodimentsinclude using the structured light images to infer depth informationregarding the scene; and in tagging, or manipulating, the visible imagesusing information regarding depth acquired based on the structured lightimages.

In embodiments, gestures inferred may include one-thumb-up;two-thumbs-up; a finger swipe; a two-finger swipe; a three-finger swipe;a four-finger-swipe; a thumb plus one finger swipe; a thumb plus twofinger swipe; etc. In embodiments, gestures inferred may includemovement of a first digit in a first direction; and of a second digit ina substantially opposite direction. Gestures inferred may include atickle.

Sensing of the intensity of light incident on an object may be employedin a number of applications. One such application includes estimation ofambient light levels incident upon an object so that the object's ownlight-emission intensity can be suitable selected. In mobile devicessuch as cell phones, personal digital assistants, smart phones, and thelike, the battery life, and thus the reduction of the consumption ofpower, are of importance. At the same time, the visual display ofinformation, such as through the use of a display such as those based onLCDs or pixellated LEDs, may also be needed. The intensity with whichthis visual information is displayed depends at least partially on theambient illumination of the scene. For example, in very bright ambientlighting, more light intensity generally needs to be emitted by thedisplay in order for the display's visual impression or image to beclearly visible above the background light level. When ambient lightingis weaker, it is feasible to consume less battery power by emitting alower level of light from the display.

As a result, it is of interest to sense the light level near or in thedisplay region. Existing methods of light sensing often include asingle, or a very few, light sensors, often of small area. This can leadto undesired anomalies and errors in the estimation of ambientillumination levels, especially when the ambient illumination of thedevice of interest is spatially inhomogeneous. For example, shadows dueto obscuring or partially obscuring objects may—if they obscure one or afew sensing elements—result in a display intensity that is less brightthan desirable under the true average lighting conditions.

Embodiments include realization of a sensor, or sensors, that accuratelypermit the determination of light levels. Embodiments include at leastone sensor realized using solution-processed light-absorbing materials.Embodiments include sensors in which colloidal quantum dot filmsconstitute the primary light-absorbing element. Embodiments includesystems for the conveyance of signals relating to the light levelimpinging on the sensor that reduce, or mitigate, the presence of noisein the signal as it travels over a distance between a passive sensor andactive electronics that employ the modulation of electrical signals usedin transduction. Embodiments include systems that include (1) thelight-absorbing sensing element; (2) electrical interconnect for theconveyance of signals relating to the light intensity impinging upon thesensing element; and (3) circuitry that is remote from thelight-absorbing sensing element, and is connected to it via theelectrical interconnect, that achieves low-noise conveyance of thesensed signal through the electrical interconnect. Embodiments includesystems in which the length of interconnect is more than one centimeterin length. Embodiments include systems in which interconnect does notrequire special shielding yet achieve practically useful signal-to-noiselevels.

Embodiments include sensors, or sensor systems, that are employed,singly or in combination, to estimate the average color temperatureilluminating the display region of a computing device. Embodimentsinclude sensors, or sensor systems, that accept light from a wideangular range, such as greater than about +20° to normal incidence, orgreater than about +30° to normal incidence, or greater than about +40°to normal incidence. Embodiments include sensors, or sensor systems,that include at least two types of optical filters, a first type passingprimarily a first spectral band, a second type passing primarily asecond spectral band. Embodiments include using information from atleast two sensors employing at least two types of optical filters toestimate color temperature illuminating the display region, or a regionproximate the display region.

Embodiments include systems employing at least two types of sensors.Embodiments include a first type constituted of a first light-sensingmaterial, and a second type constituted of a second light-sensingmaterial. Embodiments include a first light-sensing material configuredto absorb, and transduce, light in a first spectral band, and a secondlight-sensing material configured to transduce a second spectral band.Embodiments include a first light-sensing material employing a pluralityof nanoparticles having a first average diameter, and a secondlight-sensing material employing a plurality of nanoparticles have asecond average diameter. Embodiments include a first diameter in therange of approximately 1 nm to approximately 2 nm, and a second diametergreater than about 2 nm.

Embodiments include methods of incorporating a light-sensing materialinto, or onto, a computing device involving ink-jet printing.Embodiments include using a nozzle to apply light-sensing material overa defined region. Embodiments include defining a primary light-sensingregion using electrodes. Embodiments include methods of fabricatinglight sensing devices integrated into, or onto, a computing deviceinvolving: defining a first electrode; defining a second electrode;defining a light-sensing region in electrical communication with thefirst and the second electrode. Embodiments include methods offabricating light sensing devices integrated into, or onto, a computingdevice involving: defining a first electrode; defining a light-sensingregion; and defining a second electrode; where the light sensing regionis in electrical communication with the first and the second electrode.

Embodiments include integration at least two types of sensors into, oronto, a computing device, using ink-jet printing. Embodiments includeusing a first reservoir containing a first light-sensing materialconfigured to absorb, and transduce, light in a first spectral band; andusing a second reservoir containing a second light-sensing materialconfigured to absorb, and transduce, light in a second spectral band.

Embodiments include the use of differential or modulated signaling inorder to substantially suppress any external interference. Embodimentsinclude subtracting dark background noise.

Embodiments include a differential system depicted in FIG. 22. FIG. 22shows an embodiment of a three-electrode differential-layout system 700to reduce external interferences with light sensing operations. Thethree-electrode differential-layout system 700 is shown to include alight sensing material covering all three electrodes 701, 703, 705. Alight-obscuring material 707 (Black) prevents light from impinging uponthe light-sensing material in a region that is electrically accessedusing the first electrode 701 and the second electrode 703. Asubstantially transparent material 709 (Clear) allows light to impingeupon the light-sensing material in a substantially distinct region thatis electrically accessed using the second electrode 703 and the thirdelectrode 705. The difference in the current flowing through theClear-covered electrode pair and the Black-covered electrode pair isequal to the photocurrent—that is, this difference does not include anydark current, but instead is proportional to the light intensity, withany dark offset substantially removed.

Embodiments include the use of a three-electrode system as follows. Eachelectrode consists of a metal wire. Light-absorbing material may be inelectrical communication with the metal wires. Embodiments include theencapsulation of the light-absorbing material using a substantiallytransparent material that protects the light-absorbing material fromambient environmental conditions such as air, water, humidity, dust, anddirt. The middle of the three electrodes may be biased to a voltage V1,where an example of a typical voltage is about 0 V. The two outerelectrodes may be biased to a voltage V2, where a typical value is about3 V. Embodiments include covering a portion of the device usinglight-obscuring material that substantially prevents, or reduces, theincidence of light on the light-sensing material.

The light-obscuring material ensures that one pair of electrodes seeslittle or no light. This pair is termed the dark, or reference,electrode pair. The use of a transparent material over the otherelectrode pair ensures that, if light is incident, it is substantiallyincident upon the light-sensing material. This pair is termed the lightelectrode pair.

The difference in the current flowing through the light electrode pairand the dark electrode pair is equal to the photocurrent—that is, thisdifference does not include any dark current, but instead isproportional to the light intensity, with any dark offset substantiallyremoved.

In embodiments, these electrodes are wired in twisted-pair form. In thismanner, common-mode noise from external sources is reduced or mitigated.Referring to FIG. 23, electrodes 801, 803, 805 with twisted pair layout800, the use of a planar analogue of a twisted-pair configuration leadsto reduction or mitigation of common-mode noise from external sources.

In another embodiment, biasing may be used such that the light-obscuringlayer may not be required. The three electrodes may be biased to threevoltages V1, V2, and V3. In one example, V1=6 V, V2=3 V, V3=0 V. Thelight sensor between 6 V and 3 V, and that between 0 V and 3 V, willgenerate opposite-direction currents when read between 6 V and 0 V. Theresultant differential signal is then transferred out in twisted-pairfashion.

In embodiments, the electrode layout may itself be twisted, furtherimproving the noise-resistance inside the sensor. In this case, anarchitecture is used in which an electrode may cross over another.

In embodiments, electrical bias modulation may be employed. Analternating bias may be used between a pair of electrodes. Thephotocurrent that flows will substantially mimic the temporal evolutionof the time-varying electrical biasing. Readout strategies includefiltering to generate a low-noise electrical signal. The temporalvariations in the biasing include sinusoidal, square, or other periodicprofiles. For example, referring to FIG. 24, an embodiment oftime-modulated biasing 900 a signal 901 applied to electrodes to reduceexternal noise that is not at the modulation frequency. Modulating thesignal in time allows rejection of external noise that is not at themodulation frequency.

Embodiments include combining the differential layout strategy with themodulation strategy to achieve further improvements in signal-to-noiselevels.

Embodiments include employing a number of sensors having differentshapes, sizes, and spectral response (e.g., sensitivities to differentcolors). Embodiments include generating multi-level output signals.Embodiments include processing signals using suitable circuits andalgorithms to reconstruct information about the spectral and/or otherproperties of the light incident.

Advantages of the disclosed subject matter include transfer of accurateinformation about light intensity over longer distances than wouldotherwise be possible. Advantages include detection of lower levels oflight as a result. Advantages include sensing a wider range of possiblelight levels. Advantages include successful light intensitydetermination over a wider range of temperatures, an advantageespecially conferred when the dark reference is subtracted using thedifferential methods described herein.

Embodiments include a light sensor including a first electrode, a secondelectrode, and a third electrode. A light-absorbing semiconductor is inelectrical communication with each of the first, second, and thirdelectrodes. A light-obscuring material substantially attenuates theincidence of light onto the portion of light-absorbing semiconductorresiding between the second and the third electrodes, where anelectrical bias is applied between the second electrode and the firstand third electrodes and where the current flowing through the secondelectrode is related to the light incident on the sensor.

Embodiments include a light sensor including a first electrode, a secondelectrode, and a light-absorbing semiconductor in electricalcommunication with the electrodes wherein a time-varying electrical biasis applied between the first and second electrodes and wherein thecurrent flowing between the electrodes is filtered according to thetime-varying electrical bias profile, wherein the resultant component ofcurrent is related to the light incident on the sensor.

Embodiments include the above embodiments where the first, second, andthird electrodes consists of a material chosen from the list: gold,platinum, palladium, silver, magnesium, manganese, tungsten, titanium,titanium nitride, titanium dioxide, titanium oxynitride, aluminum,calcium, and lead.

Embodiments include the above embodiments where the light-absorbingsemiconductor includes materials taken from the list: PbS, PbSe, PbTe,SnS, SnSe, SnTe, CdS, CdSe, CdTe, Bi₂S₃, In₂S₃, In₂S₃, In₂Te₃, ZnS,ZnSe, ZnTe, Si, Ge, GaAs, polypyrolle, pentacene, polyphenylenevinylene,polyhexylthiophene, and phenyl-C61-butyric acid methyl ester.

Embodiments include the above embodiments where the bias voltages aregreater than about 0.1 V and less than about 10 V. Embodiments includethe above embodiments where the electrodes are spaced a distance betweenabout 1 μm and about 20 μm from one another.

Embodiments include the above embodiments where the distance between thelight-sensing region and active circuitry used in biasing and reading isgreater than about 1 cm and less than about 30 cm.

The capture of visual information regarding a scene, such as viaimaging, is desired in a range of areas of application. In cases, theoptical properties of the medium residing between the imaging system,and the scene of interest, may exhibit optical absorption, opticalscattering, or both. In cases, the optical absorption and/or opticalscattering may occur more strongly in a first spectral range compared toa second spectral range. In cases, the strongly-absorbing-or-scatteringfirst spectral range may include some or all of the visible spectralrange of approximately 470 nm to approximately 630 nm, and themore-weakly-absorbing-or-scattering second spectral range may includeportions of the infrared spanning a range of approximately 650 nm toapproximately 24 μm wavelengths.

In embodiments, image quality may be augmented by providing an imagesensor array having sensitivity to wavelengths longer than about a 650nm wavelength.

In embodiments, an imaging system may operate in two modes: a first modefor visible-wavelength imaging; and a second mode for infrared imaging.In embodiments, the first mode may employ a filter that substantiallyblocks the incidence of light of some infrared wavelengths onto theimage sensor.

Referring now to FIG. 25, an embodiment of a transmittance spectrum 1000of a filter that may be used in various imaging applications.Wavelengths in the visible spectral region 1001 are substantiallytransmitted, enabling visible-wavelength imaging. Wavelengths in theinfrared bands 1003 of approximately 750 nm to approximately 1450 nm,and also in a region 1007 beyond about 1600 nm, are substantiallyblocked, reducing the effect of images associated with ambient infraredlighting. Wavelengths in the infrared band 1005 of approximately 1450 nmto approximately 1600 nm are substantially transmitted, enablinginfrared-wavelength imaging when an active source having its principalspectral power within this band is turned on.

In embodiments, an imaging system may operate in two modes: a first modefor visible-wavelength imaging; and a second mode for infrared imaging.In embodiments, the system may employ an optical filter, which remainsin place in each of the two modes, that substantially blocks incidenceof light over a first infrared spectral band; and that substantiallypasses incidence of light over a second infrared spectral band. Inembodiments, the first infrared spectral band that is blocked may spanfrom about 700 nm to about 1450 nm. In embodiments, the second infraredspectral band that is substantially not blocked may begin at about 1450nm. In embodiments, the second infrared spectral band that issubstantially not blocked may end at about 1600 nm. In embodiments, inthe second mode for infrared imaging, active illuminating that includespower in the second infrared spectral band that is substantially notblocked may be employed. In embodiments, a substantiallyvisible-wavelength image may be acquired via image capture in the firstmode. In embodiments, a substantially actively-infrared-illuminatedimage may be acquired via image capture in the second mode. Inembodiments, a substantially actively-infrared-illuminated image may beacquired via image capture in the second mode aided by the subtractionof an image acquired during the first mode. In embodiments, aperiodic-in-time alternation between the first mode and second mode maybe employed. In embodiments, a periodic-in-time alternation betweenno-infrared-illumination, and active-infrared-illumination, may beemployed. In embodiments, a periodic-in-time alternation betweenreporting a substantially visible-wavelength image, and reporting asubstantially actively-illuminated-infrared image, may be employed. Inembodiments, a composite image may be generated which displays, inoverlaid fashion, information relating to the visible-wavelength imageand the infrared-wavelength image. In embodiments, a composite image maybe generated which uses a first visible-wavelength color, such as blue,to represent the visible-wavelength image; and uses a secondvisible-wavelength color, such as red, to represent theactively-illuminated infrared-wavelength image, in a manner that isoverlaid.

In image sensors, a nonzero, nonuniform, image may be present even inthe absence of illumination, (in the dark). If not accounted for, thedark images can lead to distortion and noise in the presentation ofilluminated images.

In embodiments, an image may be acquired that represents the signalpresent in the dark. In embodiments, an image may be presented at theoutput of an imaging system that represents the difference between anilluminated image and the dark image. In embodiments, the dark image maybe acquired by using electrical biasing to reduce the sensitivity of theimage sensor to light. In embodiments, an image sensor system may employa first time interval, with a first biasing scheme, to acquire asubstantially dark image; and a second time interval, with a secondbiasing scheme, to acquire a light image. In embodiments, the imagesensor system may store the substantially dark image in memory; and mayuse the stored substantially dark image in presenting an image thatrepresents the difference between a light image and a substantially darkimage. Embodiments include reducing distortion, and reducing noise,using the method.

In embodiments, a first image may be acquired that represents the signalpresent following reset; and a second image may be acquired thatrepresents the signal present following an integration time; and animage may be presented that represents the difference between the twoimages. In embodiments, memory may be employed to store at least one oftwo of the input images. In embodiments, the result difference image mayprovide temporal noise characteristics that are consistent withcorrelated double-sampling noise. In embodiments, an image may bepresented having equivalent temporal noise considerable less than thatimposed by sqrt(kTC) noise.

Embodiments include high-speed readout of a dark image; and of a lightimage; and high-speed access to memory and high-speed image processing;to present a dark-subtracted image to a user rapidly.

Embodiments include a camera system in which the interval between theuser indicating that an image is to be acquired; and in which theintegration period associated with the acquisition of the image; is lessthan about one second. Embodiments include a camera system that includesa memory element in between the image sensor and the processor.

Embodiments include a camera system in which the time in between shotsis less than about one second.

Embodiments include a camera system in which a first image is acquiredand stored in memory; and a second image is acquired; and a processor isused to generate an image that employs information from the first imageand the second image. Embodiments include generating an image with highdynamic range by combining information from the first image and thesecond image. Embodiments include a first image having a first focus;and a second image having a second focus; and generating an image fromthe first image and the second image having higher equivalent depth offocus.

Hotter objects generally emit higher spectral power density at shorterwavelengths than do colder objects. Information may thus be extractedregarding the relative temperatures of objects imaged in a scene basedon the ratios of power in a first band to the power in a second band.

In embodiments, an image sensor may comprise a first set of pixelsconfigured to sense light primarily within a first spectral band; and asecond set of pixels configured to sense light primarily within a secondspectral band. In embodiments, an inferred image may be reported thatcombines information from proximate pixels of the first and second sets.In embodiments, an inferred image may be reported that provides theratio of signals from proximate pixels of the first and second sets.

In embodiments, an image sensor may include a means of estimating objecttemperature; and may further include a means of acquiringvisible-wavelength images. In embodiments, image processing may be usedto false-color an image representing estimated relative objecttemperature atop a visible-wavelength image.

In embodiments, the image sensor may include at least one pixel havinglinear dimensions less than approximately 2 μm×2 μm.

In embodiments, the image sensor may include a first layer providingsensing in a first spectral band; and a second layer providing sensingin a second spectral band.

In embodiments, visible images can be used to present a familiarrepresentation to users of a scene; and infrared images can provideadded information, such as regarding temperature, or pigment, or enablepenetration through scattering and/or visible-absorbing media such asfog, haze, smoke, or fabrics.

In cases, it may be desired to acquire both visible and infrared imagesusing a single image sensor. In cases, registration among visible andinfrared images is thus rendered substantially straightforward.

In embodiments, an image sensor may employ a single class oflight-absorbing light-sensing material; and may employ a patterned layerabove it that is responsible for spectrally-selective transmission oflight through it, also known as a filter. In embodiments, thelight-absorbing light-sensing material may providehigh-quantum-efficiency light sensing over both the visible and at leasta portion of the infrared spectral regions. In embodiments, thepatterned layer may enable both visible-wavelength pixel regions, andalso infrared-wavelength pixel regions, on a single image sensorcircuit.

In embodiments, an image sensor may employ two classes oflight-absorbing light-sensing materials: a first material configured toabsorb and sense a first range of wavelengths; and a second materialconfigured to absorb and sense a second range of wavelengths. The firstand second ranges may be at least partially overlapping, or they may notbe overlapping.

In embodiments, two classes of light-absorbing light-sensing materialsmay be placed in different regions of the image sensor. In embodiments,lithography and etching may be employed to define which regions arecovered using which light-absorbing light-sensing materials. Inembodiments, ink-jet printing may be employed to define which regionsare covered using which light-absorbing light-sensing materials.

In embodiments, two classes of light-absorbing light-sensing materialsmay be stacked vertically atop one another. In embodiments, a bottomlayer may sense both infrared and visible light; and a top layer maysense visible light principally.

In embodiments, an optically-sensitive device may include: a firstelectrode; a first light-absorbing light-sensing material; a secondlight-absorbing light-sensing material; and a second electrode. Inembodiments, a first electrical bias may be provided between the firstand second electrodes such that photocarriers are efficiently collectedprimarily from the first light-absorbing light-sensing material. Inembodiments, a second electrical bias may be provided between the firstand second electrodes such that photocarriers are efficiently collectedprimarily from the second light-absorbing light-sensing material. Inembodiments, the first electrical bias may result in sensitivityprimarily to a first wavelength of light. In embodiments, the secondelectrical bias may result in sensitivity primarily to a secondwavelength of light. In embodiments, the first wavelength of light maybe infrared; and the second wavelength of light may be visible. Inembodiments, a first set of pixels may be provided with the first bias;and a second set of pixels may be provided with the second bias;ensuring that the first set of pixels responds primarily to a firstwavelength of light, and the second set of pixels responds primarily toa second wavelength of light.

In embodiments, a first electrical bias may be provided during a firstperiod of time; and a second electrical bias may be provided during asecond period of time; such that the image acquired during the firstperiod of time provides information primarily regarding a firstwavelength of light; and the image acquired during the second period oftime provides information primarily regarding a second wavelength oflight. In embodiments, information acquired during the two periods oftime may be combined into a single image. In embodiments, false-colormay be used to represent, in a single reported image, informationacquired during each of the two periods of time.

In embodiments, a focal plane array may consist of a substantiallylaterally-spatially uniform film having a substantiallylaterally-uniform spectral response at a given bias; and having aspectral response that depends on the bias. In embodiments, a spatiallynonuniform bias may be applied, for example, different pixel regions maybias the film differently. In embodiments, under a givenspatially-dependent biasing configuration, different pixels may providedifferent spectral responses. In embodiments, a first class of pixelsmay be responsive principally to visible wavelengths of light, while asecond class of pixels may be responsive principally to infraredwavelengths of light. In embodiments, a first class of pixels may beresponsive principally to one visible-wavelength color, such as blue;and a second class of pixels may be responsive principally to adistinctive visible-wavelength color, such as green; and a third classof pixels may be responsive principally to a distinctivevisible-wavelength color, such as red.

In embodiments, an image sensor may comprise a readout integratedcircuit, at least one pixel electrode of a first class, at least onepixel electrode of a second class, a first layer of optically sensitivematerial, and a second layer of optically sensitive material. Inembodiments, the image sensor may employ application of a first bias forthe first pixel electrode class; and of a second bias to the secondpixel electrode class.

In embodiments, those pixel regions corresponding to the first pixelelectrode class may exhibit a first spectral response; and of the secondpixel electrode class may exhibit a second spectral response; where thefirst and second spectral responses are significantly different. Inembodiments, the first spectral response may be substantially limited tothe visible-wavelength region. In embodiments, the second spectralresponse may be substantially limited to the visible-wavelength region.In embodiments, the second spectral response may include both portionsof the visible and portions of the infrared spectral regions.

In embodiments, it may be desired to fabricate an image sensor havinghigh quantum efficiency combined with low dark current.

In embodiments, a device may consist of: a first electrode; a firstselective spacer; a light-absorbing material; a second selective spacer;and a second electrode.

In embodiments, the first electrode may be used to extract electrons. Inembodiments, the first selective spacer may be used to facilitate theextraction of electrons but block the injection of holes. Inembodiments, the first selective spacer may be an electron-transportlayer. In embodiments, the light-absorbing material may includesemiconductor nanoparticles. In embodiments, the second selective spacermay be used to facilitate the extraction of holes but block theinjection of electrons. In embodiments, the second selective spacer maybe a hole-transport layer.

In embodiments, only a first selective spacer may be employed. Inembodiments, the first selective spacer may be chosen from the list:TiO₂, ZnO, and ZnS. In embodiments, the second selective spacer may beNiO. In embodiments, the first and second electrode may be made usingthe same material. In embodiments, the first electrode may be chosenfrom the list: TiN, W, Al, and Cu. In embodiments, the second electrodemay be chosen from the list: ZnO, Al:ZnO, ITO, MoO₃, Pedot, andPedot:PSS.

In embodiments, it may be desired to implement an image sensor in whichthe light-sensing element can be configured during a first interval toaccumulate photocarriers; and during a second interval to transferphotocarriers to another node in a circuit.

Embodiments include a device comprising: a first electrode; a lightsensing material; a blocking layer; and a second electrode.

Embodiments include electrically biasing the device during a firstinterval, known as the integration period, such that photocarriers aretransported towards the first blocking layer; and where photocarriersare stored near the interface with the blocking layer during theintegration period.

Embodiments include electrically biasing the device during a secondinterval, known as the transfer period, such that the storedphotocarriers are extracted during the transfer period into another nodein a circuit.

Embodiments include a first electrode chosen from the list: TiN, W, Al,Cu. In embodiments, the second electrode may be chosen from the list:ZnO, Al:ZnO, ITO, MoO₃, Pedot, and Pedot:PSS. In embodiments, theblocking layer be chosen from the list: HfO₂, Al₂O₃, NiO, TiO₂, and ZnO.

In embodiments, the bias polarity during the integration period may beopposite to that during the transfer period. In embodiments, the biasduring the integration period may be of the same polarity as that duringthe transfer period. In embodiments, the amplitude of the bias duringthe transfer period may be greater than that during the integrationperiod.

Embodiments include a light sensor in which an optically sensitivematerial functions as the gate of a silicon transistor. Embodimentsinclude devices comprising: a gate electrode coupled to a transistor; anoptically sensitive material; a second electrode. Embodiments includethe accumulation of photoelectrons at the interface between the gateelectrode and the optically sensitive material. Embodiments include theaccumulation of photoelectrons causing the accumulation of holes withinthe channel of the transistor. Embodiments include a change in the flowof current in the transistor as a result of a change in photoelectronsas a result of illumination. Embodiments include a change in currentflow in the transistor greater than 1000 electrons/s for everyelectron/s of change in the photocurrent flow in the optically sensitivelayer. Embodiments include a saturation behavior in which the transistorcurrent versus photons impinged transfer curve has a sublineardependence on photon fluence, leading to compression and enhanceddynamic range. Embodiments include resetting the charge in the opticallysensitive layer by applying a bias to a node on the transistor thatresults in current flow through the gate during the reset period.

Embodiments include combinations of the above image sensors, camerasystems, fabrication methods, algorithms, and computing devices, inwhich at least one image sensor is capable of operating in globalelectronic shutter mode.

In embodiments, at least two image sensors, or image sensor regions, mayeach operate in global shutter mode, and may provide substantiallysynchronous acquisition of images of distinct wavelengths, or fromdifferent angles, or employing different structured light.

Embodiments include implementing correlated double-sampling in theanalog domain. Embodiments include so doing using circuitry containedwithin each pixel. FIG. 26 shows an example schematic diagram of acircuit 1100 that may be employed within each pixel to reduce noisepower. In embodiments, a first capacitor 1101 (C1) and a secondcapacitor 1103 (C2) are employed in combination as shown. Inembodiments, the noise power is reduced according to the ratio C2/C1.

FIG. 27 shows an example schematic diagram of a circuit 1200 of aphotoGate/pinned-diode storage that may be implemented in silicon. Inembodiments, the photoGate/pinned-diode storage in silicon isimplemented as shown. In embodiments, the storage pinned diode is fullydepleted during reset. In embodiments, C1 (corresponding to the lightsensor's capacitance, such as quantum dot film in embodiments) sees aconstant bias.

In embodiments, light sensing may be enabled through the use of a lightsensing material that is integrated with, and read using, a readoutintegrated circuit. Example embodiments of same are included in U.S.Provisional Application No. 61/352,409, entitled, “Stable, SensitivePhotodetectors and Image Sensors Made Therefrom Including Circuits forEnhanced Image Performance,” and U.S. Provisional Application No.61/352,410, entitled, “Stable, Sensitive Photodetectors and ImageSensors Made Therefrom Including Processes and Materials for EnhancedImage Performance,” both filed Jun. 8, 2010, which are herebyincorporated by reference in their entirety.

In embodiments, a method of gesture recognition is provided where themethod includes acquiring a stream, in time, of at least two images fromeach of at least one camera module; acquiring a stream, in time, of atleast two signals from each of at least one light sensor; and conveyingthe at least two images and the at least two signals to a processor, theprocessor being configured to generate an estimate of a gesture'smeaning, and timing, based on a combination of the at least two imagesand the at least two signals.

In embodiments, the at least one light sensor includes a light-absorbingmaterial having an absorbance, across the visible wavelength region ofabout 450 nm to about 650 nm, of less than about 30%.

In embodiments, the light-absorbing material includes PBDTT-DPP, thenear-infrared light-sensitive polymerpoly(2,60-4,8-bis(5-ethylhexylthienyl)benzo-[1,2-b;3,4-b]dithiophene-alt-5-dibutyloctyl-3,6-bis(5-bromothiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4-dione).

In embodiments, the at least one light sensor includes a light-sensingmaterial capable of sensing infrared light.

In embodiments, the method includes modulating a light source using atleast one code selected from spatial codes and temporal codes.

In embodiments, the light source has an emission wavelength in the rangeof about 900 nm to about 1000 nm.

In one embodiment, a camera system includes a central imaging arrayregion, at least one light-sensing region outside of the central imagingarray region, a first mode, referred to as imaging mode, and a secondmode, referred to as sensing mode. The electrical power consumed in thesecond mode is at least 10 times lower than the electrical powerconsumed in the first mode.

In embodiments, the at least one light sensor includes a light-sensingmaterial capable of sensing infrared light.

In embodiments, light impinging on the light-sensing material is to bemodulated.

In embodiments, a portion of light impinging on the light-sensingmaterial is to be generated using a light emitter device having anemission wavelength in the range of about 800 nm to about 1000 nm.

In embodiments, the central imaging array includes at least sixmegapixels.

In embodiments, the central imaging array comprises pixels less thanapproximately 2 μm in width and approximately 2 μm in height.

In one embodiment, an image sensor circuit includes a central imagingarray region having a first field of view; and at least onelight-sensing region outside of the central imaging array region havinga second field of view. The second field of view is less than half,measured in angle, the field of view of the first field of view.

In one embodiment, an integrated circuit includes a substrate, an imagesensing array region occupying a first region of said semiconductorsubstrate and including a plurality of optically sensitive pixelregions, a pixel circuit for each pixel region, each pixel circuitcomprising a charge store and a read-out circuit, and a light-sensitiveregion outside of the image sensing array region. The image sensingarray region having a first field of view and the light-sensitive regionhaving a second field of view; the angle of the second field of view isless than half of the angle of the first field of view.

In embodiments, at least one of the image sensing array and thelight-sensitive region outside of the image sensing array regionincludes a light-sensing material capable of sensing infrared light.

In embodiments, light impinging on at least one of the image sensingarray and the light-sensitive region outside of the image sensing arrayregion is to be modulated.

In embodiments, a portion of light impinging on at least one of theimage sensing array and the light-sensitive region outside of the imagesensing array region is to be generated using a light emitter devicehaving an emission wavelength in the range of about 800 nm to about 1000nm.

In embodiments, the image sensing array includes at least sixmegapixels.

In embodiments, the image sensing array comprises pixels less thanapproximately 2 μm in width and approximately 2 μm in height.

In one embodiment, an image sensor includes a central imaging arrayregion to provide pixelated sensing of an image, in communication with aperipheral region that includes circuitry to provide biasing, readout,analog-to-digital conversion, and signal conditioning to the pixelatedlight sensing region. An optically sensitive material overlies theperipheral region.

In embodiments, the at least one light sensor includes a light-sensingmaterial capable of sensing infrared light.

In embodiments, light impinging on the light-sensing material is to bemodulated.

In embodiments, a portion of light impinging on the light-sensingmaterial is to be generated using a light emitter device having anemission wavelength in the range of about 800 nm to about 1000 nm.

In embodiments, the central imaging array includes at least sixmegapixels.

In embodiments, the central imaging array comprises pixels less thanapproximately 2 μm in width and approximately 2 μm in height.

In embodiments, the optically sensitive material is chosen to include atleast one material from a list, the list including silicon, colloidalquantum dot film, and a semiconducting polymer.

In embodiments, the optically sensitive material is fabricated on afirst substrate, and is subsequently incorporated onto the centralimaging array region.

The various illustrations of the methods and apparatuses provided hereinare intended to provide a general understanding of the structure ofvarious embodiments and are not intended to provide a completedescription of all the elements and features of the apparatuses andmethods that might make use of the structures, features, and materialsdescribed herein.

A person of ordinary skill in the art will appreciate that, for this andother methods disclosed herein, the activities forming part of variousmethods may, in certain cases, be implemented in a differing order, aswell as repeated, executed simultaneously, or substituted one foranother. Further, the outlined acts, operations, and apparatuses areonly provided as examples, and some of the acts and operations may beoptional, combined into fewer acts and operations, or expanded intoadditional acts and operations without detracting from the essence ofthe disclosed embodiments.

The present disclosure is therefore not to be limited in terms of theparticular embodiments described in this application, which are intendedas illustrations of various aspects. Many modifications and variationscan be made, as will be apparent to a person of ordinary skill in theart upon reading and understanding the disclosure. Functionallyequivalent methods and apparatuses within the scope of the disclosure,in addition to those enumerated herein, will be apparent to a person ofordinary skill in the art from the foregoing descriptions. Portions andfeatures of some embodiments may be included in, or substituted for,those of others. Many other embodiments will be apparent to those ofordinary skill in the art upon reading and understanding the descriptionprovided herein. Such modifications and variations are intended to fallwithin a scope of the appended claims. The present disclosure is to belimited only by the terms of the appended claims, along with the fullscope of equivalents to which such claims are entitled. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only and is not intended to belimiting.

In addition, in the foregoing Detailed Description, it may be seen thatvarious features are grouped together in a single embodiment for thepurpose of streamlining the disclosure. This method of disclosure is notto be interpreted as limiting the claims. Thus, the following claims arehereby incorporated into the Detailed Description, with each claimstanding on its own as a separate embodiment.

What is claimed is:
 1. A pixel circuit, comprising: a first electrodecoupled to a reset transistor and to a first region of an opticallysensitive layer; a second electrode coupled to a pixel sense node and toa second region of the optically sensitive layer, the electrical pathfrom the first electrode, through the optically sensitive layer, andinto the second electrode, being configured to function as a variableresistor.
 2. The pixel circuit of claim 1, wherein, in a first mode, thevariable resistor exhibits a resistance of less than 10⁹ ohms.
 3. Thepixel circuit of claim 2, wherein, in the first mode, the sense node isreset to a potential determined by the reset transistor.
 4. The pixelcircuit of claim 1, wherein, in a second mode, the variable resistorexhibits a resistance exceeding 10¹⁶ ohms.
 5. The pixel circuit of claim4, wherein, in the second mode, the optically sensitive layer issubstantially fully depleted of free carriers.
 6. The pixel circuit ofclaim 4, wherein, in the second mode, the sense node potential changesat a rate related to the optical signal illuminating the opticallysensitive layer.
 7. The pixel circuit of claim 1, wherein, in a thirdmode, the first electrode is electrically coupled to the output of afeedback amplifier.
 8. The pixel circuit of claim 7, wherein thefeedback amplifier is configured to impose a voltage on the sense nodethat is specified to within a noise power that is appreciably less thankT/C.
 9. The pixel circuit of claim 1, wherein the optically sensitivelayer is sensitive to any of one or more wavelength regions of regionsincluding infrared, visible, and ultraviolet regions of theelectromagnetic spectrum.
 10. The pixel circuit of claim 1, wherein theoptically sensitive layer includes one or more types of quantum dotnanocrystals.
 11. The pixel circuit of claim 11, wherein at least two ofthe one or more types of quantum dot nanocrystals are at least partiallyfused.
 12. The pixel circuit of claim 1, wherein the optically sensitivelayer includes a combination of at least two types of quantum dots, eachof the at least two types of quantum dots including a distinctsemiconductor material.
 13. The pixel circuit of claim 1, wherein theoptically sensitive layer includes a combination of at least two typesof quantum dots, each of the at least two types of quantum dots havingdistinct properties.
 14. The pixel circuit of claim 1, wherein theoptically sensitive layer includes at least one of an opticallysensitive semiconducting polymer selected from a list of polymersincluding MEH-PPV, P3OT, and P3HT.
 15. The pixel circuit of claim 1,wherein the optically sensitive layer includes a polymer-quantum dotmixture having one or more types of quantum dots sensitive to differentportions of the electromagnetic spectrum.
 16. A pixel circuit,comprising: a reset transistor having a gate, a source, and a drain; anoptically sensitive material to couple to a first electrode and a secondelectrode, the first electrode being in electrical communication withthe source; wherein during a first, hard reset interval, a residual ofprior integration periods is reset, and during a second, feedback-basedsoft reset interval, an electrical potential is set to a level that isdefined to within a noise power that is appreciably less than kT/C. 17.A pixel circuit, comprising: an optically sensitive layer having a firstelectrode and a second electrode, the first electrode being inelectrical communication with a switch; wherein in a integration periodmode, the switch is configured to provide a DC bias to the opticallysensitive layer, and during a feedback-reset period mode, the switch isconfigured to couple to a feedback reset device, the feedback resetdevice being configured to impose a reset to a defined reset voltagelevel that is specified to within a noise power that is appreciably lessthan kT/C.